OPERATING SEGMENT INFORMATION (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) segment	Jun. 30, 2016 USD ($)
Segment Reporting Information [Line Items]
Number of Operating Segments | segment			3
Capacity purchase arrangements	100.00%		100.00%
Operating revenues
Passenger, Mainline	$ 1,556	$ 1,036	$ 2,828	$ 1,963
Passenger, Regional	251	227	463	433
Total passenger revenue	1,807	1,263	3,291	2,396
CPA revenues	0	0	0	0
Freight and mail	32	27	56	51
Other - net revenue	263	204	504	394
Total Operating Revenues	2,102	1,494	3,851	2,841
Operating expenses
Operating Expenses, Excluding Fuel	1,265	875	2,509	1,765
Economic fuel	344	201	683	368
Total Operating Expenses	1,609	1,076	3,192	2,133
Nonoperating Income (Expense)
Interest income	9	7	16	13
Interest expense	(26)	(9)	(51)	(22)
Other	3	4	7	13
Nonoperating Income (Expense) Total	(14)	2	(28)	4
Income (loss) before income tax	479	420	631	712
Air Group Adjusted [Member]
Operating revenues
Passenger, Mainline	1,556	1,036	2,828	1,963
Passenger, Regional	251	227	463	433
Total passenger revenue	1,807	1,263	3,291	2,396
CPA revenues	0	0	0	0
Freight and mail	32	27	56	51
Other - net revenue	263	204	504	394
Total Operating Revenues	2,102	1,494	3,851	2,841
Operating expenses
Operating Expenses, Excluding Fuel	1,241	861	2,445	1,751
Economic fuel	342	211	671	380
Total Operating Expenses	1,583	1,072	3,116	2,131
Nonoperating Income (Expense)
Interest income	9	7	16	13
Interest expense	(26)	(9)	(51)	(22)
Other	3	4	7	13
Nonoperating Income (Expense) Total	(14)	2	(28)	4
Income (loss) before income tax	505	424	707	714
Alaska Mainline [Member]
Operating revenues
Passenger, Mainline	1,556	1,036	2,828	1,963
Passenger, Regional	0	0	0	0
Total passenger revenue	1,556	1,036	2,828	1,963
CPA revenues	0	0	0	0
Freight and mail	31	26	54	49
Other - net revenue	244	184	466	356
Total Operating Revenues	1,831	1,246	3,348	2,368
Operating expenses
Operating Expenses, Excluding Fuel	1,026	679	2,024	1,380
Economic fuel	304	180	596	324
Total Operating Expenses	1,330	859	2,620	1,704
Nonoperating Income (Expense)
Interest income	9	6	16	12
Interest expense	(23)	(4)	(45)	(16)
Other	3	3	6	10
Nonoperating Income (Expense) Total	(11)	5	(23)	6
Income (loss) before income tax	490	392	705	670
Alaska Regional [Member]
Operating revenues
Passenger, Mainline	0	0	0	0
Passenger, Regional	251	227	463	433
Total passenger revenue	251	227	463	433
CPA revenues	0	0	0	0
Freight and mail	1	1	2	2
Other - net revenue	19	19	36	36
Total Operating Revenues	271	247	501	471
Operating expenses
Operating Expenses, Excluding Fuel	206	192	406	378
Economic fuel	39	31	75	56
Total Operating Expenses	245	223	481	434
Nonoperating Income (Expense)
Interest income	0	0	0	0
Interest expense	0	0	0	0
Other	0	0	0	0
Nonoperating Income (Expense) Total	0	0	0	0
Income (loss) before income tax	26	24	20	37
Horizon [Member]
Operating revenues
Passenger, Mainline	0	0	0	0
Passenger, Regional	0	0	0	0
Total passenger revenue	0	0	0	0
CPA revenues	108	110	205	213
Freight and mail	0	0	0	0
Other - net revenue	1	1	2	2
Total Operating Revenues	109	111	207	215
Operating expenses
Operating Expenses, Excluding Fuel	116	101	219	206
Economic fuel	0	0	0	0
Total Operating Expenses	116	101	219	206
Nonoperating Income (Expense)
Interest income	0	1	0	1
Interest expense	(3)	(4)	(5)	(5)
Other	1	0	1	0
Nonoperating Income (Expense) Total	(2)	(3)	(4)	(4)
Income (loss) before income tax	(9)	7	(16)	5
Intersegment Elimination [Member]
Operating revenues
Passenger, Mainline	0	0	0	0
Passenger, Regional	0	0	0	0
Total passenger revenue	0	0	0	0
CPA revenues	(108)	(110)	(205)	(213)
Freight and mail	0	0	0	0
Other - net revenue	(1)	0	0	0
Total Operating Revenues	(109)	(110)	(205)	(213)
Operating expenses
Operating Expenses, Excluding Fuel	(107)	(111)	(204)	(213)
Economic fuel	(1)	0	0	0
Total Operating Expenses	(108)	(111)	(204)	(213)
Nonoperating Income (Expense)
Interest income	0	0	0	0
Interest expense	0	(1)	(1)	(1)
Other	(1)	1	0	3
Nonoperating Income (Expense) Total	(1)	0	(1)	2
Income (loss) before income tax	(2)	1	(2)	2
Special Revenue and Charges [Member]
Operating revenues
Passenger, Mainline	0	0	0	0
Passenger, Regional	0	0	0	0
Total passenger revenue	0	0	0	0
CPA revenues	0	0	0	0
Freight and mail	0	0	0	0
Other - net revenue	0	0	0	0
Total Operating Revenues	0	0	0	0
Operating expenses
Operating Expenses, Excluding Fuel	24	14	64	14
Economic fuel	2	(10)	12	(12)
Total Operating Expenses	26	4	76	2
Nonoperating Income (Expense)
Interest income	0	0	0	0
Interest expense	0	0	0	0
Other	0	0	0	0
Nonoperating Income (Expense) Total	0	0	0	0
Income (loss) before income tax	$ (26)	$ (4)	$ (76)	$ (2)